This invention relates to a man-machine link for use in supplying a coordinate representing digital signal from a tablet device to an information handling system which may be a personal computer or a work station. It is to be noted in connection with the expression of a "man-machine" link that this invention relates to a link for use in combination with the tablet device.
The tablet device is described, for example, in a report contributed by M. R. Davis et al of the Rand Corporation, California, to Proceedings of the 1964 Fall Joint Computer Conference, pages 325-331, under the title of "The Rand Tablet: a Man-Machine Graphical Communication Device," and in another report which was contributed by James F. Teixeira et al of Sylvania Electronic Systems, Massachusetts, to 1968 Spring Joint Computer Conference, pages 315-321, and is given a title of "The Sylvania data tablet: A new approach to graphic data input." In the manner which will later be described a little more in detail, such a tablet device comprises a tablet and a stylus. When the stylus is brought into contact with the tablet at a point, the device produces a digital signal representative of the abscissa and the ordinate of the point as a coordinate count.
On supplying the digital signal to the above-exemplified information handling system, the tablet device is connected to a port of an interface for the system. When the port is exclusively used in other data communication, a new interface is necessary for the digital signal of the tablet device.
A "mouse" is a tablet device of a sort which has recently been developed into practical use. Information handling systems have become widely used, which are equipped with particular interface for the mice. Ordinarily, the interface for the mouse is incapable of directly dealing with absolute values of the abscissa and the ordinate. Instead, the interface deals only with a two-phase pulse signal of a phase difference which corresponds to an increment or a decrement, or a positive or a negative increment, in each of the abscissa and the ordinate. The information handling system is therefore inoperative when a conventional tablet device is connected directly to an interface for a mouse. In fact, a conventional tablet device must be used instead of a mouse when it is difficult to supply the information handling system with patterns of certain kinds.